Excretory Case Study 3*

Urolithiasis

 

Daniel, a thirty-two year old history instructor, was in his office preparing notes for an upcoming seminar presentation when he was struck with a very sudden and intense pain in his side and lower back. He remained at his desk, breathing deeply, and the pain began to recede. Five minutes later, the pain was not as severe but Daniel was still uncomfortable and decided to call his physician.   After asking Daniel a few questions about his symptoms, the doctor requested an abdominal x-ray, several blood tests, and urinalysis. As Daniel supplied the urine sample he was disturbed to notice that the urine had a pinkish cast. The physician returned and informed Daniel that he had a kidney stone which, based on its size, should pass on its own within a day or so. The doctor told Daniel that he should rest at home until the stone passed, drink at least 2-3 quarts of water each day, and strain his urine in order to retrieve the stone for analysis. The doctor also gave Daniel a prescription for pain medication.  Daniel passed the stone the following morning.  Analysis of the stoneŐs composition revealed that it was a calcium stone. DanielŐs blood and urine tests had also shown high calcium levels.

 

The presence of kidney stones, or urinary caliculi, in the urinary tract is called urolithiasis. These stones form from materials that are excreted by the kidneys. Normally these excreted materials stay dissolved in urine, but in some individuals they form precipitates that can develop into kidney stones. Kidney stones can form from several different substances. Kidney stone analysis, blood tests, and urinalysis all assist a physician in determining how best to avoid the development of future stones. Calcium stones are most common, comprising between 80 and 90 percent of urinary caliculi. The calcium stones are formed from calcium phosphate or calcium oxalate, and persons predisposed to developing these stones are often instructed to decrease calcium and oxalate intake. In some cases, medications are prescribed that decrease calcium excretion by the kidneys or alter urine pH, a factor in kidney stone formation.  The pain associated with the blockage of the urinary tract by a kidney stone is called renal colic and can be very intense. Treatment depends primarily on the size of the stone.

Questions:

 

1.         List the components of the urinary tract from the renal pelvis outward. Explain the role of the nephron in excretory system biochemistry.

 

2.         Why would water facilitate the passage of kidney stones?

 

3.         Why would water aid in the prevention of developing future kidney stones?

 

4.         List the three stages in the formation of urine and describe each stage with regard to the structures involved and the direction substance transport.

 

5.         The glomerular filtrate concentration of calcium (Ca+2) is about 4 mEq/L. The concentration of calcium in the urine is about 5 mEq/L. How would you explain this difference?

 

*adapted from McGraw Hill Online Learning Center, Essentials of Anatomy and Physiology,3rd ed.Seely/Stephens/Tate